1. Field of the Invention
The present invention relates generally to a fail safe hydraulic actuator system which is linear or rotary and is capable of returning an externally associated valve to its fail safe or inoperative position in the event of loss of electrical power to the system.
Even though the loss of electrical power is maintained, the improved manifold block of the present invention enables one to operate a manual 4 way valve and a hand pump to open the fail safe closed valve that would otherwise remain closed as long as the electrical power is unavailable to the system.
2. The Prior Art
Linear actuators with piston means displaced by fluid or air pressure are typically used to control the opening and closing of valves, e.g., gate valves, globe valves, sluice gates and cone valves.
Many situations exist where electrically operated control mechanisms, such as the valves just noted, and the like, if locked in an operative position by an interruption of electric power, can create awkward, difficult, and even hazardous conditions.
The Wright U.S. Pat. No. 5,301,505 discloses a fail safe hydraulic actuator system, particularly one featuring a linear actuator, which upon loss of electric power instantly and automatically returns the control mechanism which is being monitored to the inoperative or closed position.
Other examples of fail safe electrical actuator systems include the following:
PatenteeU.S. Pat. No.DateWright4,757,684Jul. 19, 1988Wright5,087,846Feb. 11, 1992Wright5,205,200Apr. 27, 1993Wright5,275,193Jan. 4, 1994WrightDes 479,576Sep. 9, 2003
All of these prior art documents and disclosures are each herewith incorporated by reference.
However, each of these prior art structures and systems has the disadvantage that as long as the power failure exists, that it is not possible to use a hand pump manual valve structure to activate the linear actuator to move in such a direction as to open the closed valve which was closed as part of the automatic fail safe procedure and fail safe system.